BACKGROUND Diabetes mellitus (DM) is one of the risk factors for progression from latent to active tuberculosis. However, the effect of DM on subsequent tuberculosis treatment is still inconclusive. OBJECTIVE To compare tuberculosis treatment outcomes and the rate of drug resistance of tuberculosis patients with or without DM. METHODS This case-control study was conducted between 2005 and 2015 at the only tuberculosis ward in Israel. All 80 tuberculosis patients who had DM and were hospitalized during the study period were included in this study, as were a randomized sample of 213 tuberculosis patients without DM. Demographic, clinical, and laboratory data were collected from patient files in the hospital and clinics after discharge. RESULTS Tuberculosis patients with DM were more often older and more likely to be Israeli citizens with a lower socioeconomic status than patients without DM. No statistically significant differences were found in clinical presentation, radiological findings, and sputum smear tests between the two groups. Culture converting times were prolonged in patients with DM compared to normoglycemic patients. Multidrug drug resistance tuberculosis was more common among normoglycemic tuberculosis patients than tuberculosis patients with DM (9.2% vs. 1.6%, P = 0.12). Treatment success rates were 76.2% and 83.1% for tuberculosis patients with or without DM, respectively (P = 0.18). DM was not statistically significant in the multivariate analysis predicting treatment success, which controlled for age, citizenship, compliance, addictions, and chronic diseases. CONCLUSIONS The presence of DM does not necessarily affect tuberculosis treatment outcomes as long as treatment compliance is optimal.